Diseconomies of scale
Diseconomies of scale are the rising unit costs that can appear when an organisation grows too large to coordinate efficiently.
Growth is supposed to lower costs. Past a certain size, it can start raising them instead.
Diseconomies of scale are the rising average costs a firm can suffer when it grows too large, so that getting bigger makes each unit more expensive rather than cheaper. They are the reason the cost advantages of size do not continue without limit, and why the biggest firm is not always the most efficient.
Why bigness can cost
The main sources are organisational rather than technical. As a firm grows, coordinating its activities becomes harder and slower. Layers of management multiply, communication degrades, decisions take longer, and the distance between the top and the front line widens. Bureaucracy expands to manage the complexity, consuming resources without adding output. Motivation can fall as individuals feel lost in a vast machine. None of these show up in the engineering of production; they emerge from the difficulty of running something large.
The U-shaped cost curve
Together, economies and diseconomies of scale give the average cost curve its characteristic U shape. As output rises from small, scale economies pull unit cost down; beyond an efficient size, diseconomies push it back up. The bottom of the U is the scale at which a firm produces most cheaply, and it is not infinite. Industries differ in where that point lies, which is part of why some support a few giants and others a crowd of mid-sized firms.
The practical warning
Diseconomies of scale are the standing rebuke to the assumption that growth always helps. Firms that expand past their efficient size, through acquisition or ambition, can find their costs rising and their advantages slipping, even as revenue grows. Recognising the limit, and sometimes choosing not to grow further, or to break a sprawling organisation into smaller, more manageable units, can be the cost-conscious choice.
Diseconomies of scale are a reminder that organisations are not just production functions but human systems, and that the costs of coordinating people eventually overtake the savings of producing in bulk. Bigger is cheaper only up to a point, and past it, only dearer.